Sunan an-Nasa'i

Mutarrif bin 'Abdullah bin Ash-Shikhkhir narrated from his father that: the Messenger of Allah (ﷺ) said, concerning one who fasted for the rest of his life: "He neither fasted nor broke his fast." 'Ata said: "someone who heard him told me that Ibn 'Umar (said) that the Prophet (ﷺ) said: 'Whoever fasts every day of his life, then he has not fasted."